I have a 90 gallon sps dominate tank and i have some sps that are light in color. Every time i test for NO3 it detects 0. Can low nutrients be my problem? Elos Planet II light fixture 4 t-5 blues on from 10:30 a.m to 10:30 pm and 2x150 mh on from 12:30 p.m to 8.30 p.m Ca 430 alk 8.5 mag 1400 temp ranges between 78 to 80 s.g 1.025